This is a proposal to define the role of blood oxygen affinity as a determinant of oxygen supply to tissue. Specific proposals deal with effect of decreased and increased P50, and other perturbations of oxygen transport, on (1) cardiac output and its distribution, as measured by radioactive microspheres, in resting and exercising rats; (2) isolated hindlimb oxygen consumption and muscle function during rest and excercise: (3) myocardial function during coronary perfusion at various flow rates and at various levels of cardiac work; and (4) electroencephalogram and cerebral oxygen consumption in the isolated brain. BIBLIOGRAPHIC REFERENCES: Woodson, R.D., Malmberg, P. and Hlastala, M.P.: Effect of increased blood O2 affinity on experimental hemorrhagic shock. Clin. Res. 23: 436A, 1975. Woodson, R.D., Malmberg, P. and Hlastala, M.P.: Effect of raised blood oxygen affinity (1ow P50) on oxygen transport and tolerance of hemorrhagic shock. Fed. Proc. 35: 838, 1976.